I am very familiar with Eastern Black Rat Snakes. The ones I have seen in Virginia are for the most part always black with a white underbelly that contains grayish rectangular blotches starting a little way past the chin. They run about 1/3of the way down its body. At that point what you see is by then is just a gray color. I put up a link that will show you the typical pattern.

By the new classification system, there are Eastern Rat Snakes, Pantherophis alleghaniensis, Central Rat Snakes, Pantherophis spiloides, and Western Rat Snakes, Pantherophis obsoleta. On the East Coast, The Black, Yellow, and Everglades Rats are now considered one species.
Here are the Taxonomic Notes
Burbrink et al. (2000) and Burbrink (2001) examined genetic and morphological variation in Elaphe obsoleta and determined that the nominal subspecies do not represent evolutionary lineages and should no longer be recognized. Further, these authors identified three clades within E. obsoleta, corresponding to populations (1) west of the Mississippi River (western clade), (2) east of the Mississippi River and west of the Appalachian Mountains and Apalachicola River (central clade), and (3) east of the Appalachians and the Apalachicola River (eastern clade). Burbrink (2000) recognized the three clades as distinct species: E. obsoleta (western clade), E. spiloides (central clade), and E. alleghaniensis (eastern clade). In mapping the distribution of the species, Burbrink indicated a very large area of "taxonomic uncertainty" extending from New England to northern Georgia. In this region the distribution of E. alleghaniensis was deemed "somewhat questionable with regard to hybridization with members of Elaphe spiloides." Va Black Rat